The invention relates to a rail for guiding at least one of two sheet-metal edge margins, more especially longitudinal edge margins of can bodies, which are to be welded together, having
a supporting body with a longitudinal groove, which comprises two lateral surfaces which are at least approximately parallel to each other and a base surface which is at least approximately perpendicular to the lateral surfaces, and
an insert of hard material which is fastened in the longitudinal groove and butts against its base surface.
Such a rail in the form of a so-called Z rail is known from Document WO 90/02016. This Z rail has an upper and a lower supporting body, in which an upper or lower longitudinal groove respectively is incorporated from one side. In each of the longitudinal grooves is fastened an insert in which a guide groove for a sheet metal edge is formed. The inserts are composed of tungsten carbide or material such as silicon nitride, aluminium oxide or another non-abrasive, electrically non-conducting material and are fastened in the supporting body by sticking; immediately thereafter, their guide grooves are formed by grinding. When the inserts are worn out, they have to be replaced together with the supporting body, as a renewal of the inserts on the spot is not possible.
From DE 3432505 Al is known as a Z rail which has two supporting bodies, arranged one over the other, to which slide bodies are fastened. The slide bodies are profiled stepwise and arranged to engage in each other in such a way that together they form two longitudinal grooves situated one above the other and overlapping one another for guiding a sheet-metal edge margin in each case. Overlap of the two edge margins and the spacing of their heights can be varied within certain limits by adjusting the slide bodies. The manufacture of these stepwise profiled slide bodies is costly. If the bodies are composed of hard material, for example, tungsten carbide or a ceramic material, they are then sensitive to shock, and there is a danger that they may break with careless clamping on the associated supporting bodies.